widget/material: [API] add description argument to IconButton

Icons have no inherent semantic meaning such as a label, so this change
adds another argument to the IconButton constructor for the client to
provide a description.

This is an API change, because it seems best to force every client to
provide semantic descriptions for icon buttons.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

widget/material/button.go

@@ -46,6 +46,7 @@ type IconButtonStyle struct {
 	Size        unit.Value
 	Inset       layout.Inset
 	Button      *widget.Clickable
+	Description string
 }
 
 func Button(th *Theme, button *widget.Clickable, txt string) ButtonStyle {
@@ -72,7 +73,7 @@ func ButtonLayout(th *Theme, button *widget.Clickable) ButtonLayoutStyle {
 	}
 }
 
-func IconButton(th *Theme, button *widget.Clickable, icon *widget.Icon) IconButtonStyle {
+func IconButton(th *Theme, button *widget.Clickable, icon *widget.Icon, description string) IconButtonStyle {
 	return IconButtonStyle{
 		Background:  th.Palette.ContrastBg,
 		Color:       th.Palette.ContrastFg,
@@ -80,6 +81,7 @@ func IconButton(th *Theme, button *widget.Clickable, icon *widget.Icon) IconButt
 		Size:        unit.Dp(24),
 		Inset:       layout.UniformInset(unit.Dp(12)),
 		Button:      button,
+		Description: description,
 	}
 }